(a) Technical Field
The present invention relates to a method and an apparatus for forming a coating layer with a nano multi-layer, particularly a method and apparatus which controls the direction of crystal growth so as to improve the corrosion resistance and electrical conductivity of a coating layer.
(b) Background Art
In general, a plasma coating technique is used to coat a 3rd material onto an untreated material using plasma phenomenon under a vacuum condition so as to add mechanical and functional characteristics that the untreated material does not possess. Plasma coating techniques are commonly divided to CVD (Chemical vapor deposition) and PVD (Physical vapor deposition).
Among PVD techniques, vacuum deposition, sputtering, ion plating and the like are broadly used. Ion plating is further classified to various coating methods according to the plasma activation method and coating material ionization methods.
Arc ion plating is a technique in which a coating material (target) is vapor ionized as a negative electrode using arc discharge. This technique has been beneficially used for producing hard coatings because it provides a rapid coating rate due to its rapid evaporation rate, thus providing good productivity as well as high ionization, and high crash and migration energies.
However, while the coating material formed by arc ion plating generally has excellent corrosion resistance, it has low electrical conductivity, which is problematic. For example, while CrN formed using an arc ion plating technique has excellent corrosion and wear resistant properties, it is low in electrical conductivity. In attempt to improve the electrical conductivity, a Cr2N phase has been formed on a CrN coating layer, and the resulting coating has been used as a surface coating material for a component requiring corrosion resistance and electrical conductivity, such as a fuel cell separator. However, the electrical conductivity provided by such coatings is somewhat insufficient.
What is needed is a coating layer and a method for forming a coating layer which provides a base material with improved corrosion resistance and electrical conductivity.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.